Re: Samsung syncmaster t220 Powers on no screen.
Well.... I tried to mimic the reflow curve, with the help of an infrared thermometer. The connectors were somewhat protected with tin foil.
- At first I let the oven preheat to ~150ºC
- Then I placed the board and let it there a couple of minutes
- After that, I turned on the second heating element.
I would say the temperature was ~200-230ºC. But, anyway, it's hard to say.
The big capacitors were probably damaged due to high temperature
In any case... that...
Moki_X
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Last Activity: 12-21-2014, 01:32 PM
Joined: 12-13-2014
Location: Spain
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Re: Samsung syncmaster t220 Powers on no screen.
Ok.... I decided to discard the screen.
But before I wanted to try a last and fun bullet: The homemade poorman's reflow technique.
I put the logic board in an oven, and I left it there several minutes. I roasted it a bit. I know
The connectors almost melted and now is brownish.
But... Now I'm getting 5.15V at 5V_MAIN, the BL_EN (2.5V) and 5V_PANEL signals appeared and they are consistent with the ON/OFF keypress.
Tomorrow I'll assembly the whole screen and see what happens....Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
The service manual is "SAMSUNG LTW22HS LTW22GS LTW20HS CH LTW20GS T220 T220G T220N T220GN T200 T200G T200N T200GN"
So, from the test that I performed:
- Power board is working OK.
- No visible signs of damage.
- The problem is on Logic board, since it's not sending the correct signals.
- 3.3V and 1.8V are present and powering the scale chip.
Maybe a "software" problem? corrupt EEPROM or something like that?
I say that because the scaling chip...Last edited by Moki_X; 12-16-2014, 08:35 AM.Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
Ok. I have taken a look at the service manual and I identified the part that converts 5V_MAIN into 5V_PANEL
0.69V at PANEL_EN.
At the MOSFET I have 4.06V at GATE, 4.47V at SOURCE and 0V at DRAIN. Regardless if LVDS ribbon is connected or not.
So, MOSFET is blown? Here I attach a diagram. Could you confirm my guess, please?
(MOSFET's datahseet: [url]https://cdn.badcaps-static.com/pdfs/d797847856bdaa07324ba3ea60120791.pdf[/url])
(Thank you for the service manual :P)...Last edited by Moki_X; 12-15-2014, 07:08 PM.Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
When power on, voltage at:
- Both ends of the fuse
- 5V testpoint
- 5V_PANEL testpoint at the logic board
are all 0V
Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
There's yet a hidden board!
Ok, I took a picture and I tested the F1 SMD device with a multimeter. I guess it's a fuse and it reads 0.1 ohm, so I think it's not blown.
Should I take new measurements with the power on? Do you need any other picture?...Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
I can turn on the backlights by manually triggering the BL_ENABLE signal.
Measurements are made with the LVDS ribbon cable [B]attached[/B] at the logic board and the CCFL lamps [B]detached[/B] from the power lamp, as it's physically difficult to hold all the circuits together.
I don't know how to locate the T-CON board SMD fuse....
Yeah, 4.38V for 5V_MAIN seems to low to me.
3.16V is actually 3.28V (my fault... I measured it with the LVDS cable detached).Re: Samsung syncmaster t220...Last edited by Moki_X; 12-14-2014, 03:09 PM.Leave a comment:
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Re: Samsung syncmaster t220 Powers on no screen.
Hello!
I have the same problem: Power on (red LED is on), but no screen (no backlight and no image!)
- I've checked the voltages at the connector:
1 -> 3.9V (BL_ADJ_PWM)
2 -> 14V (+14V)
3 -> 0V (GND)
4 -> 0V (GND)
5 -> 5.24V (5V_IP_1)
6 -> 5.24V (5V_IP_2)
7 -> 3.5V (BL_ADJ_ANALOG)
8 -> 0V (BL_EN)
9 -> 3.29V (+3.3V)
10 -> 2.95V (LED)
11 -> 3.04V (KEY1_OUT)
12 -> 1.77V (KEY2_OUT)
-...Last edited by Moki_X; 12-14-2014, 11:42 AM.Leave a comment:
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